1. Field of the Invention
This invention relates generally to impact type moving carriage printers and more particularly to such printers which are required to operate in a harsh environment.
2. Description of the Prior Art
Electric typewriters are known which have circuitry for automatically turning off power after a predetermined period of non-use. Examples of such apparatus include: U.S. Pat. No. 3,354,372, entitled, "Delay Responsive Shut-Off Device For Operationally Vibrating Electric Equipment", which issued to J. O. Beasley on Nov. 21, 1967; and U.S. Pat. No. 3,753,004, entitled, "Electric Typewriter Automatic On-Off Switch", which issued to Paul C. Dominic on Aug. 14, 1973. In the last mentioned patent, an embodiment is disclosed which includes an impact sensor for detecting impact on the spacer bar for turning the typewriter on. There is no provision, however, for temporarily interrupting the printing operation during a period of unusually high vibration or shock and thereafter continuing operation without illegible character printing and/or losing data upon the termination of the unusually high vibration or shock level.
Also known in the art of electric typewriters and high speed printers is the inclusion of input data storage means for acting as an input buffer for data fed into the system at a greater rate than it can be utilized by the printing mechanism. Typical examples of such apparatus are: U.S. Pat. No. 3,718,243, entitled, "Apparatus For Storing Typing Commands Given In Too Rapid Succession By Keys", issued to K. Chvatlinsky, on Feb. 27, 1973; U.S. Pat. No. 3,924,722, entitled, "Typewriter With Electronic Keyboard", issued to J. L. Wienhold, on Dec. 9, 1975; U.S. Pat. No. 3,973,662, entitled, "Acceleration Control System For High Speed Printer", issued to J. R. Fulton on Aug. 10, 1976; U.S. Pat. No. 4,203,678, entitled "Electronic Control Circuit For A High Speed Bi-directional Printer", issued to L. A. Nordstrom, et al. on May 20, 1980; and U.S. Pat. No. 4,405,245, entitled, "Variable Speed Signal Printing Apparatus", which issued to T. Fukushima on Sept. 20, 1983. While such apparatus purports to operate in the respective manners disclosed, they do not operate so as to provide a temporary storage for printing data during the occurrence of unusually high vibration and/or shock levels which have a tendency to move the print head from a known valid print position.
Accordingly, it is an object of the present invention to provide an improvement in printing apparatus.
Another object of the invention is to provide an improvement in impact dot matrix printing mechanisms.
A further object of the invention is to provide an improvement in dot matrix printers which are capable of operating in harsh environments.